(CNN) -- The United States has announced new sanctions against Iran targeted at the country's nuclear and missile programs -- identifying more than twenty companies and several individuals allegedly involved with those programs.

The U.S. Treasury Department says the measures begin to implement the recent U.N. Security Council Resolution 1929 and highlight "Iran's use of its financial sector, shipping industry and Islamic Revolutionary Guards Corps to carry out and mask its proliferation activities."

Announcing the measures at the White House, Treasury Secretary Tim Geithner said they "are designed to deter other governments and foreign financial institutions from dealing with these entities and thereby supporting Iran's illicit activities."

"In the coming weeks, we will continue to increase the financial pressure on Iran," he said.

The sanctions mean that all transactions involving any of the targeted entities and any U.S. individual are prohibited, and any assets the entities may have under U.S. jurisdiction are frozen.

Robert Einhorn, a senior U.S. State Department official, has been appointed to work with other governments to ensure international sanctions are enforced.

Among the entities targeted for sanctions are Post Bank of Iran and five front companies associated with the Islamic Republic of Iran Shipping Lines.

The U.S. Treasury says Post Bank has acted on behalf of another entity -- Bank Sepah -- that had previously been designated for providing financial services to Iran's missile industry. As Iran's state-owned banks face increasing sanctions, the government began using Post Bank to facilitate trade involving Iran's defense industries, the Treasury Department said.

It also alleges the bank facilitated millions of dollars worth of business between Hong Kong Electronics and other overseas beneficiaries. Hong Kong Electronics was designated last year for providing support to North Korea's Tanchon Commercial Bank.

U.S. Treasury Under-Secretary for Terrorism and Financial Intelligence Stuart Levey, who is largely responsible for desigining the sanctions, said the United States expected Iran would "scramble" to develop new front companies and banks to circumvent the sanctions, but that the U.S. government would continue to go after them.

"As we keep exposing this kind of deception, we keep exposing risks that you have to do business with Iran," he said.

Levey said the names of the companies being designated will be sent to every financial institution in the world. The hope is banks and private-sector companies will stop doing business with Iran once they realize the risks involved, which has been the scenario when the U.S. designated other Iranian entities.

"Many companies around the world have been and will choose not to do business with Iran," Levey said. "We have seen in the past when we added entities, it has an effect."

Other companies being targeted include Rah Sahel and Sepanir Oil and Gas Engineering, two subsidiaries of the engineering arm of the Revolutionary Guards. The two companies were also sanctioned on June 9 with the adoption of U.N. Security Council Resolution 1929. The United States maintains the Revolutionary Guards Corps has links to Iran's ballistic missile programs and is closely tied to developing and testing the Shahab-3 missile.

Levey said that a total of 22 petroleum, energy and insurance companies owned or controlled by the Iranian government had been designated in this latest round of sanctions, including 17 located outside Iran.

Also targeted in these latest sanctions are Mohammad Ali Jafari, commander-in-chief of the Revolutionary Guards since September 2007, and Mohammad Reza Naqdi, a senior commander in the Guards who is already under U.N. sanctions for being involved in efforts to evade the sanctions imposed under previous U.N. resolutions.

"It is our view that no IRGC entity should have a place in the financial system," Levey said.

The United States measures also designate a Tehran-based company, Javedan Mehr Toos. The U.S. alleges that since 2009, the company has sought to obtain a variety of nuclear-related equipment on the international market, including magnets which can be used in centrifuges.

The Treasury Department says that since being targeted for sanctions, the Islamic Republic of Iran Shipping Lines (IRISL) has looked to front companies to help it evade scrutiny. The measures announced Wednesday identified 27 new vessels as "blocked" due to their connection to IRISL. Of the five shipping companies newly identified, two are based in Hong Kong.

Geithner said financial pressure on Iran would be maintained. "Iran will never cease looking for new ways to evade our sanctions. So our efforts must be ongoing and unrelenting."